Adaptive digital audio encoding system

Abstract

An encoding system employing a novel perceptual spectrum difference estimation device improves the coding efficiency and audio quality of a digitized audio signal. The system comprises M number of encoding means arranged in parallel for encoding the input digital audio signal of a current frame, respectively; M number of decoding means arranged in parallel for decoding each of the encoded digital audio signals; a first estimator for estimating a power density spectrum for a difference signal between the input digital audio signal and each of the decoded digital audio signals; a second estimator for estimating a power density spectrum for the input digital audio signal of the current frame and for determining a masking threshold therefor based on the power density spectrum for the input digital audio signal; a third estimator for estimating a set of perceptual spectrum distances based on the power density spectrum for each of the difference signals and the masking threshold; and a circuit for selecting an encoded digital audio signal having a smallest perceptual spectrum distance.

What is claimed is: 
     
       1. A system for adaptively encoding an input digital audio signal having a plurality of frames, which comprises: M number of encoding means arranged in parallel for encoding the input digital audio signal in a current frame, respectively;   M number of decoding means arranged in parallel for decoding each of the encoded digital audio signals;   first estimation means for estimating a power density spectrum of a difference signal between the input digital audio signal and each of the decoded digital audio signals;   second estimation means for estimating a power density spectrum of the input digital audio signal in the current frame and for determining a masking threshold thereof based on the power density spectrum of the input digital audio signal;   third estimation means for deriving a set of perceptual spectrum distances based on the power density spectrum of each of the difference signals and the masking threshold; and   means for selecting an encoded digital audio signal having a smallest perceptual spectrum distance.